Lightning and gounding

Frank, W3LPL, wrote:
>Mike,
>
>I'm sure the readers of this newsgroup would appreciate it if u
>could provide evidence and details of damage sustained by tower
>foundations as a result of a lightning strike. Thanx!
>
>73!FrankW3LPL
Frank, et al:
I have no first hand evidence, all of my towers are properly
grounded with ground rods external to the tower base. However I
can provide the following technical reference:
"Telecommunications Electrical Protection" by Edward P. Carter
Copyright 1985 AT&T Technologies, Inc.
I quote from chapter 9.5, "The antenna structure is a prime
target for lightning, and although metallic antenna horns and
dishes are unlikely to be damaged by a direct stroke, the entire
structure consitutes an excellent transmission path for
conducting high current into the equipment building. Stroke
current will also seek a path to ground via tower footings and guy
anchors. At these points, explosive damage may occur unless
alternate paths are provided to bypass the current and reduce
voltage differences."
The author goes on to say, "Towers should be grounded to reduce
the amount of stroke current entering the station area and to
prevent possible lightning damage to foundations and guy anchor
footings."
While this text is primarily aimed at the protection of
commerial telecommunications facilities (including microware
radio sites), I believe that it is relevent to ham radio
installations.
The bottom line is that the concrete base of the tower supports
the entire weight of the tower PLUS the downward force exerted
by the guy wires. Using the tower base as the ONLY ground for
the tower may compromise the tower base's structural integrity
resulting in a potentially dangerous situation. Likewise, not
providing a separate path to ground at the guy anchor points may
compromise the structural integrity of the guy anchor.
I would hate to see anyone killed or seriously hurt because they
didn't think it necessay to install a protective ground system
for their tower.
73 de mike
Michael.Zeug@ameritech.com
p.s. You may be able to order a copy of this text by calling the
AT&T Customer Information Center on 1-800-432-6600. Ask for
select code 350-060.
>From Robert Penneys <penneys@brahms.udel.edu> Thu Jun 22 03:16:05 1995
From: Robert Penneys <penneys@brahms.udel.edu> (Robert Penneys)
Subject: HELP!! Need 6m rig for Field Day!!
Message-ID: <199506220216.WAA00836@brahms.udel.edu>
Help! Our 6 meter rig for Field Day became unavailable. We need to borrow
a rig capable of SSB and CW which will run off 12v batteries. If you have
one, I will have it picked up Thursday, and send it back to you UPS, Federal
or whatever, Monday.
We really need help on this one. Please call me at work 800 644-4476 between
9:30 AM and 5:30 PM Eastern time.
Tnx, Bob
Bob Penneys, WN3K Internet: penneys@brahms.udel.edu
Frankford Radio Club N.E.R.D.S. (club call KB3BIJ for now)
Work: Ham Radio Outlet, Delaware
>From GOOSE WD8LLD <GOOSTER@delphi.com> Thu Jun 22 03:44:24 1995
From: GOOSE WD8LLD <GOOSTER@delphi.com> (GOOSE WD8LLD)
Subject: radial wire
Message-ID: <01HRZG8VQ8UQ8X0X9V@delphi.com>
On 21-JUN-1995 13:09:23.7 n0dh said to GOOSTER
> <---- Begin Included Message ---->
> From: mraz@maverick.aud.alcatel.com (Kris I. Mraz)
> Reply-To: mraz@maverick.aud.alcatel.com (Kris I. Mraz)
> To: cq-contest@tgv.com
> Subject: radial wire
> Aluminum fence wire can be purchased very cheaply. Can this be used for
> radial wires in a phased vertical system? I believe it is about 18
>gauge wire.
> 73
> Kris AA5UO
> mraz@aud.alcatel.com
> <---- End Included Message ---->
> Works fine...lasts long time!
> N0DH
> dit dit
Kris,
Only see two problems using aluminum wire for radials.
1) If you live in an area where there is a lot of freezing and
thawing of ground (which I assume you don't with a 5 call) you will end up
with a lot of little pieces of broken radila in the ground after about 2-3
years due to the stretching of the soft aluminum. So for northern U.S this
is not practical since your ground system will not last very long.
2) This is the major problem with aluminum. Bonding it to some
dissimilar metal is a big headache. If you just plan on using serews or
bolts to attach it to the ground side of the coax or tower buss, make sure
to us some form of antioxidant (like Penetrox) to prevent the electrolysis
and eventual corrosion from the other metal surface. Make sure to use
stainless steel hardware to prevent corrosion betweeen the aluminum and the
hardware.
I have used electric fence wire for radials on my 160 vertical although
it was the galvanized steel variety and you can get lots for a small amount
of bucks. This was nivce because the cost and the having to replace it
only about every 6 yrs made it attractive at the time. However, when i
replace the 160 gnd system this year, am going with #12 ot #14 soft drawn
copper. We use this in the B'cast industry (abeit the #10 variety)
and it will last about 20 years.
73..........de Goose, WD8LLD "gooster@delphi.com"
>From Rich L. Boyd" <rlboyd@CapAccess.org Thu Jun 22 03:38:30 1995
From: Rich L. Boyd" <rlboyd@CapAccess.org (Rich L. Boyd)
Subject: Contest Free Zone ??
Message-ID: <Pine.3.07.9506212229.E2144-9100000@cap1.capaccess.org>
Right, we're not on the bands that much. Contesters spend the vast
majority of their time building (and re-building) their station, ending up
with the best stations in ham radio. After all that hard work "off-line"
we deserve the small fraction of the total available time that we take up
(on the air).
Rich Boyd KE3Q
>From wrt@eskimo.com (Bill Turner W7LZP) Thu Jun 22 03:47:09 1995
From: wrt@eskimo.com (Bill Turner W7LZP) (Bill Turner W7LZP)
Subject: radial wire
Message-ID: <199506220247.AA24628@mail.eskimo.com>
At 11:12 AM 6/21/95 CDT, Kris I. Mraz wrote:
>Aluminum fence wire can be purchased very cheaply. Can this be used for
>radial wires in a phased vertical system? I believe it is about 18 gauge wire.
>
>
>73
>Kris AA5UO
>mraz@aud.alcatel.com
>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
When it's new it would no doubt be fine, but buried in the ground you'll
have corrosion quick and plenty!! Due to the "skin effect" at RF, losses
will go up. Exactly how much I couldn't say, but I'd avoid it like the
plague. Use insulated wire -- either enamel or plastic works great. The
insulation is transparent to RF, and it will slow down corrosion
considerably. Here in Seattle, the Boeing surplus store is a fabulous
source of cheap wire. Literally tons of it. Check around in your area for
similar outlets. Buy it by the thousand-foot reel for pennies on the
dollar, but never, never pay list price for brand new stuff!!
18 gauge or even smaller is fine. The current is divided amongst all of the
radials, so effectively they're all in parallel with each other, so the loss
is low. Put down lots of radials, nice long ones, and when you have enough,
put down some more... :-) Your signal reports will be your reward.
Incidentally, don't bury the radials very deep, if at all. You want the
field around the antenna to "see" the radials, not the earth. Earth is
lossy, radials aren't. Right on the surface works great if you can keep
them out of the lawnmower and not have folks tripping over them. I laid
mine out on the surface and held them down with lots of staple-like things I
made out of bailing wire. When the grass grew over them the next year, they
became practically invisible. Once in a while I find one that had an
encounter with the lawnmower, so I just lay down another. Works like a charm.
73, Bill W7LZP
wrt@eskimo.com
>From Fred Hopengarten" <k1vr@k1vr.jjm.com Wed Jun 21 02:46:43 1995
From: Fred Hopengarten" <k1vr@k1vr.jjm.com (Fred Hopengarten)
Subject: Lightning and ICE
Message-ID: <2fe77a05.k1vr@k1vr.jjm.com>
On Tue, 20 Jun 1995 13:58:49 -0600, "Bill Standerfer" KF0DJ
<bills@hpislwes.lvld.hp.com> wrote:
> Is this kind of customer "service" typical of ICE?
K1VR: Not in my experience. They've been better than good
to me.
--
Fred Hopengarten K1VR
Six Willarch Road * Lincoln, MA 01773-5105
home + office telephone: 617/259-0088 (FAX on demand)
internet: k1vr@k1vr.jjm.com
"Big antennas, high in the sky, are better than small ones, low."
>From Brian Short <ke7gh@PrimeNet.Com> Thu Jun 22 03:49:59 1995
From: Brian Short <ke7gh@PrimeNet.Com> (Brian Short)
Subject: Field Day Help
Message-ID: <199506220250.TAA14737@usr5.primenet.com>
>
> Gentlemen, I have a technical question, sil vous plait.
>
> I am setting up a last minute 1B, 1-Op Field Day from a very remote
> area of Arizona. Will run FT-890, laptop, computer keying, battery
> power, etc. The site is high, about 6000 feet, but there are no tall
> trees only short juniper and pinon pine (big shruberies). This is
> likely an advantage as there is no attenuation by the foilage, but
> it leaves me without a high support for a wire. I have constructed
> a 4'x4' base to mount a TV type tripod. I have 30 feet of mast I
> can use. The question, what antenna to use? I have already packed
> a full size 160m inverted vee, a Carolina Windom (80-10), and a half
> size G5RV (just in case). I could, of course, build something else.
> What antenna would you recommend? First choice would be one already
> built. BTW I plan to operate 20m, 40m, 80m, and would like to try
> 160 despite QRN. The 890 has the autotuner and I also have a little
> MFJ tuner for portable. Also in mothballs, I have a 40m loop, a 30m
> loop, 17m loop, and a few short dipoles for higher bands. Didn't
> see these as useful right now, but there you go.
>
> I hope the Ranchers' cattle don't graze through in the night. They roam
> freely! I can do whatever I want, too, since I own 40 acres of it
> anyway. Well, that describes the problem, degrees of freedom, etc.
> If you care to, please send me some comments, soon as I take off Friday
> morning for the 200 mile drive to DM-54, Apache County, Arizona etc.
>
> BTW: I am aware multiple 100' towers etc would be a good solution! At
> this time I have 30 feet of TV mast.
>
> My Sincere Thanks, 73, de Brian
>
>
Sorry, after my first response, I realized I forgot something! The ground
slopes off to the east pretty dramatically. Also slopes off to the west,
but not by as much. I chose the highest spot on the property and their
are rolling (small) hills. I have a view for miles and miles (literally)
for over 270 degrees of horizon. There is Mesa Redonda to the southwest,
but no ARRL sections there anyway (just may have trouble working back into
Phoenix). The shot to California is clear, but I have been mostly thinking
about EAST where I can see miles and miles.
Based on the first response, I thought these details may help.
My Sincere Thanks, Brian
>From Steve Sacco <0006901972@mcimail.com> Thu Jun 22 03:57:00 1995
From: Steve Sacco <0006901972@mcimail.com> (Steve Sacco)
Subject: LIGHTNING
Message-ID: <70950622025707/0006901972DC3EM@MCIMAIL.COM>
After being in Dallas for four days, I come home to bustling downtown
Narcoosee (the blinking yellow light on State Route 15, right next to the
Narcoosee Grocery store/Fina gas station) and see that I've missed some
wonderful discussions on SSTV and lightning.
To the SSTV comments, I've nothing to add.
I cannot say the same for the discussion on lightning, which has bordered
on being funny, if it weren't such an important subject.
I live in Central Florida, which is an area known as the "Lightning Capital
of the United States". We experience >100 days/year of lighting activity.
Lightning bolts in Central Florida are THREE times more powerful than your
"average" bolt, and also carry two to three times the current ofyour
average, every day strike. Because of this, lightning protection is a
subject on which I've done a fair amount of research. Having done this
research (which, by the way, was neither difficult nor boring), I find it
very difficult to deal with some of the ridiculous "theories" on lighting
protection I've heard and seen.
From the messages I've read - and I've just plowed through them all -
there's been only a few excellent sugestions. One of them was to purchase
the PolyPhaser book "The 'Grounds' for Lightning and EMP Protection", by
Roger R. Block. Anyone interested in this topic - and that should be
EVERYONE save a few of the West Coast USA types - should know the basic
information (as opposed to the formulas, etc) in this book by memory!
Think about it - is it REALLY a matter of "life and death" if you choose
between an FT-1000 and an IC-775 for your next rig? No.
You can't say the same thing about lightning protection!
For all of the thousands of dollars many of us spend on radios, antennas,
$1,300 Geochron clocks, Pentuim PCs, and other "essential" widgets, it's
interesting to speculate why ANYONE would be willing to let twenty-five
bucks get between them and continued ignorance on such an important
subject.
With respect to the "exploding base" myth, Mr. Block has the following to
say: (he is discussing "Ufer" grounds):
"One of the most important tests performed was under acutal lightning
conditions. The test was to see if the Ufer ground would turn the water
inside the concrete into steam and blow the foundation apart. Results
indicated that if the Ufer wire were long (20-feet minimum) and kept
approximately 3-inches from the bottom and sides of the concrete, no such
problems would occur. (In my many years of experience, I have only seen one
tower base with cracks that could be considered as lightning induced....)"
With respect to the "Don't ground anything and lighting will not hit it"
argument, Mr. Block says:
"One of the best sayings is really not a myth at all "A gounded tower is
more likely to be hit. As we say in the graph in chapter one, the taller
an object the more frequently it's struck. Why ground a tower if it means
that it is more apt to be hit? Look at it from the reverse point of view -
if a tower that isn't grounded is hit, who would have control of the
situation, the tower owner or Mother Nature? With a properly grounded
tower, the owner has control. The whole concept of lightning protection is
to control and direct the lightning surge energy so that it does the least
amount of harm or damage."
So, proper lighting protection is really a matter of CONTROL. Do you want
to ALLOW yourself to be a victim, or do you, to the best of your ability,
manage the situation to afford yourself the safest conditions possible?
Clearly, the idea of NOT grounding your station seems a bit silly when cast
in this light. NOTHING is a perfect insulator! Even a Fibreglas pole will
conduct electricity if it's covered with rain water (witness the many
VHF/UHF verticals blasted off the tops of towers every year), so pretending
that an ungrounded tower will not be struck is sheer fantasy.
Hopefully, the above quoted material didn't violate too many copyright
laws. I would submit to you that that information ALONE is worth $25!
Another tip is to make sure that all of your grounds are at the same
potential, including your house ground. This means connecting ALL of your
ground points together. I have four towers; three of them 100' or greater
in height. They are the tallest things around for miles and miles. They
ALL have ground radials with ground rods every 16', and all four towers'
grounds are tied to a common grounding point just outside the shack (where
the lightning arrestors are) and also to the house ground. I've used over
85 8' ground rods, and buried more ground wire than I even want to think
about.
It's the price you pay for not being a victim.
Oh, does anyone want to know why those wire-brush thingies sold as
"lightning protection" don't work? What about the "ground radial circle"
myth? What's the significance of 150 feet with respect to lightning
strikes?
Get the book.
Well, I guess this letter has just about ground to a halt...
73,
Steve KC2X
Narcoosee, Florida
ssacco@mcimail.com